From: Robina Suwol
Date: 04 Jan 2006
Time: 06:09:21
Remote Name: 69.149.56.50
Biological Monitoring Survey of Organophosphorus Pesticide Exposure among Pre-school Children in the Seattle Metropolitan Area
Environmental Health Perspectives Volume v.109, n.3, Mar01
Chensheng Lu, Dianne E. Knutson, Jennifer Fisker-Andersen, and Richard A. Fenske
Department of Environmental Health, University of Washington, Seattle,
Washington, USA
Abstract
In this study we assessed organophosphorus (OP) pesticide exposure among
children living in two Seattle metropolitan area communities by measuring
urinary metabolites, and identified possible exposure risk factors through a
parental interview. We recruited children in clinic and outpatient waiting
rooms. We obtained spot urine samples in the spring and fall of 1998 from
110 children ages 2-5 years, from 96 households. We analyzed urine samples for
six dialkylphosphate (DAP) compounds, the common metabolites of the OP
pesticides. Through parental interviews we gathered demographic and residential
pesticide use data. At least one of the DAP metabolites was measured in 99% of
the children, and the two predominant metabolites (DMTP
and DETP) were measured in 70-75% of the children. We found no significant
differences in DAP concentrations related to season, community, sex, age, family
income, or housing type. Median concentrations of dimethyl and diethyl DAPs were
0.11 and 0.04 µmol/L, respectively (all children). Concentrations were
significantly higher in children whose parents reported pesticide use in the
garden (0.19 vs. 0.09 µmol/L for dimethyl metabolites, p = 0.05; 0.04 vs. 0.03
µmol/L for diethyl metabolites, p = 0.02), but were not different based on
reported pet treatment or indoor residential use. Nearly all children in this
study had measurable levels of OP pesticide metabolites. Some of this exposure
was likely due to diet. Garden pesticide use was associated with elevated
metabolite levels. It is unlikely that these exposure levels would cause acute
intoxication, but the long-term health effects of such exposures are unknown. We
recommend that OP pesticide use be avoided in areas where children are likely to
play. Key words: biological monitoring, children, dialkylphosphate compounds,
organophosphorous pesticides, urine. Environ Health Perspect 109:299-303 (2001).
[Online 5 March 2001]
http://ehpnet1.niehs.nih.gov/docs/2001/109p299-303lu/abstract.html
Address correspondence to C. Lu, Box 357234, University of Washington,
Seattle, WA 98195-7234 USA. Telephone: (206) 685-9299. Fax: (206) 616-2687.
E-mail: calu@u.washington.edu We
thank S. Kong for her assistance in subject recruitment and sample collection,
T. Moate for the analytical work, and the families who participated in this
study.
This work was supported by the U.S. Environmental Protection Agency (U.S. EPA)
through Science to Achieve Results (STAR) program (grant R819186-01) and by
Cooperative Agreement U07/CCU012926-04 (Pacific Northwest Agricultural Safety
and Health Center) from the NIOSH/CDC. Its contents are solely the
responsibility of the authors and do not necessarily represent the official view
of the U.S. EPA or the National Institute for Occupational Health/Centers for
Disease Control and Prevention.
Received 11 September 2000; accepted 23 October 2000.
Introduction
Concerns regarding children's exposure to pesticides have increased in recent
years with the reported association between childhood cancers and residential
pesticide use or parental pesticide use in the workplace (1-4). According to the
National Home and Garden Pesticide Use Survey prepared by the U.S. Environmental
Protection Agency (U.S. EPA) in 1990 (5), 75% of American households use
insecticides. Children may be particularly susceptible to pesticide health
effects because of behavioral, dietary, and physiological characteristics
associated with development (6). Children's daily activities, proximity to
floors, carpets, lawns, soil, and the frequency and duration of their
hand-to-mouth activity may put them at higher risk for pesticide exposure than
adults (7). Infants and children also differ quantitatively and qualitatively
from adults in their exposure
to pesticide residues in foods (8). They have greater average daily food
consumption per unit of body weight than do adults and differ in the specific
foods that they eat. Moreover, the typical diet of infants and young children,
including a high proportion of fruits, fruit juices, milk, drinking water, and
processed foods, is less diverse than that of adults. Tissues, organs,
biological systems, and detoxification mechanisms of children are undergoing
rapid growth and development, predisposing them to potentially more severe
consequences of toxic chemicals. Organophosphorus (OP) pesticides have become a
special concern for regulatory agencies because of their widespread use, acute
toxicity, and neurotoxic properties (9). Despite the common use of pesticides in
residential environments and in agriculture, few studies have measured
children's exposure levels. Some have focused on acute poisoning incidents with
known or probable sources (10,11); others have examined low-level, chronic
pesticide exposures in agricultural communities (12-16). There are no published
studies identified to date that have examined OP pesticide exposures in children
residing in urban/suburban communities. The objectives of this study were to
assess OP pesticide exposure among children living in two different communities
in the Seattle metropolitan area using urinary dialkylphosphate (DAP) metabolite
concentrations as biomarkers, and to identify possible risk factors for OP
pesticide exposure of children through a parental interview.
Method
Study design. This cross-sectional study included repeated spot urine sample
collection and is part of a larger study that aims to assess children's exposure
to pesticides, identify risk factors, and develop strategies for pesticide
exposure reduction. Two communities located in the Seattle metropolitan area
were selected for subject recruitment. Community 1 is south of the city of
Seattle in King County. This area is urban and densely populated. The residents
in this area are predominantly lower to middle
income and many reside in multifamily dwellings. Community 2 is a suburb north
of Seattle in south Snohomish and north King counties. The area is predominantly
inhabited by middle- to upper middle-income families residing in single-family
dwellings.
Subject recruitment.
Families were recruited in the lobbies of a public-funded Women, Infants, and
Children (WIC) clinic in community 1 and in a private pediatric clinic in
community 2. The WIC clinic provides nutritional counseling and midwifery
services to families meeting certain income criteria. The pediatric clinic is a
group practice providing outpatient care. To be eligible for our study, the
child had to be toilet trained and between 2 and 5 years old. The procedures
used in the study were
reviewed and approved by the University of Washington Human Subjects Review
Committee; written consent was obtained from each parent, and oral assent was
obtained from each child.
Sample collection.
Participants included 58 children from 50 families recruited from community 1,
and 52 children from 46 families recruited from community 2. Upon recruitment,
parents were provided with polypropylene specimen cups for collecting a urine
sample at home. Commode inserts were also provided for children who were unable
to urinate directly into the specimen cup (usually females). If the insert was
to be used for sample collection, the parent was asked to transfer the urine
from the insert to the provided specimen cup. Appointments were made to pick up
the children's urine samples at their residences. In some cases, urine samples
were obtained at the clinic at the time of recruitment.
We collected two spot urine samples from each child. The first (spring) sample
was collected from 7 May to 6 June 1998 and the second (fall) from 29 September
to 18 November 1998. Spring through fall was determined to be a period of high
residential pesticide use in the Seattle area, based on information gathered
from local pest control and lawn care services and veterinarians. We selected
these sampling periods to increase the chances of obtaining urine samples with
detectable OP metabolites. For the second (fall) sampling period, specimen cups
and cover letters containing abbreviated pesticide use surveys were mailed to
all families who participated in the first sampling. Participants included 49
and 51 children who provided samples from community 1 and 2, respectively (10
children were lost to follow-up).
Sample handling.
Parents were given instructions on assisting their child to collect the
specimen. When samples were collected at the time of
recruitment, parents gave the sample to the investigator for transport to the
University of Washington laboratory. When samples were collected in their
residences, the parent was asked to place the sample in the refrigerator until
it was picked up by our staff. All samples were picked up within 48 hr of the
void, most in less than 24 hr. All urine samples were transported on ice. Urine
samples were processed immediately after arrival in the laboratory. Total sample
volume was recorded and the urine was aliquoted into three centrifuge tubes with
volumes of 5, 10, and 15 mL. Samples were stored at -20°C until analysis.
Parental interview.
An interview was administered at the time of sample pickup. We collected general
information regarding the child's age and
weight, parental occupation, and income level of the family. Questions regarding
residential environment included home ownership status, length of time at
current residence, and housekeeping practices (presence of a floor mat,
frequency of vacuuming). We gathered residential pesticide use information by
establishing whether the household had any pets, a lawn, or a
vegetable or flower garden. We asked families if a family member or a
professional had used pesticides on pets, lawn, garden, or inside their home
within the previous 6 months. We also asked which specific pesticide products
were used and asked to see them if available. When possible, we recorded the
product name, EPA registration number, date of application, and location where
the pesticide was applied. Finally, we asked questions about the child's
activities and behaviors, such as the child's frequency of hand washing,
placement of hands in the mouth, and thumb sucking. A brief follow-up
questionnaire was administered with the fall sample collection, which focused on
insecticide use since the previous sample collection.
Sample analysis. We analyzed urine samples for six common dialkylphosphate (DAP)
metabolites: dimethylphosphate (DMP), dimethylthiophosphate (DMTP),
dimethyldithiophosphate (DMDTP), diethylphosphate (DEP), diethylthiophosphate (DETP),
and diethyldithiophosphate (DEDTP). Urine samples collected in the spring
sampling period were not analyzed for DEDTP
because no analytical standard was available at that time.
Analysis was performed using a gas chromatograph equipped with a flame
photometric detector and a splitless injector (Hewlett Packard, Palo Alto, CA)
and a Supelco SPB-20 column (J&W Scientific, Folsom, CA). Sample preparation
procedures included solid phase extraction, azeotropic distillation, and
pentafluoro(methyl)benzylbromide (PFBBR) derivitization.
We determined the limit of quantitation (LOQ) for each DAP compound on the basis
of the mean recovery of the lowest fortification level minus 3 standard
deviations (SD). Metabolite residues that were less than the LOQ were designated
as < LOQ and were assigned values of 1/2 LOQ for statistical analysis. The LOQs
were 7.4 ng/mL for DMP, 6.6 ng/mL for DMTP, 1.1 ng/mL for DMDTP, 1.2 ng/mL for
DEP, 0.7 ng/ml for DETP, and 1.1 ng/mL for DEDTP. DMTP and DETP were the most
frequently detected DAP compounds in urine samples collected during the spring
(70% and 71%) and fall (74% and 71%). These results were consistent with our
previous study in which urine samples were collected from children living in an
agricultural community (13).
Data analysis. The dimethyl (DMP, DMTP, and DMDTP) and diethyl (DEP and DETP)
metabolite concentrations were converted to their molar concentrations (µmol/L)
and summed to produce a single methyl or ethyl dialkylphosphate concentration
for each sample (16). Because only one urine sample contained a detectable DEDTP
concentration, DEDTP was excluded from the data analysis.
The distributions for the dimethyl and diethyl molar concentrations were skewed
and were not effectively normalized using either a log10 or a square-root
transformation. Therefore, we performed statistical analyses with nonparametric
tests using SPSS 8.0 (SPSS Inc., Chicago, IL). A focus child was selected for
families with more than one child enrolled in the study, to remove
within-household dependence. The primary criteria for focus child selection were
contribution of two spot urine samples and acceptable creatinine measurements. A
95% confidence interval of creatinine measurement was constructed based on the
urine samples collected from this study and from a previous study of 109
children ages 2-5 years old (15). Creatinine values falling within this
confidence interval range were considered acceptable. If two children from the
same family met these criteria, selection was random.
Results
Participating families included in the analysis consisted of 50 families from
community 1 and 46 families from community 2. The mean ages of the participating
children were 3.9 years and 4.0 years for communities 1 and 2, respectively.
There were 29 male (58%) and 21 female (42%) children from community 1, and 26
males (57%) and 20 females (43%) from community 2. The
study population was predominantly Caucasian, and the ethnicity of the two
communities was similar. The socioeconomic status of the study communities,
however, differed distinctly. Community 2 participants were predominantly
upper-middle income: 96% of these families (44 families) reported annual incomes
above $35,000 and resided in single-family homes. Conversely, families recruited
from community 1 were primarily low to middle income: 88% of these families (44
families) reported annual incomes below $35,000, and 74% (37 families) resided
in multiunit buildings.
Table 1 - Dialkylphosphate concentrations (µmol/L) a in urine samples collected
from children living in two communities in the Seattle metropolitan area.
Boys b Girls b Community1 Community2 All children
Methyl c Ethyl d Methyl Ethyl Methyl Ethyl Methyl Ethyl Methyl Ethyl
Median 0.10 0.04 0.11 0.04 0.10 0.03 0.11 0.04 0.11* 0.04*
Mean 0.19 0.05 0.18 0.04 0.17 0.04 0.20 0.05 0.19 0.05
CV(%) 100 125 89 100 94 75 100 100 95 80
n 49 49 47 47 50 50 49 46 96 96
Min-Mm 0.04-0.93 0.03-0.31 0.04-0.72 0.03-0.24 0.04-0.59 0.03-0.20
0.04-0.93 0.03-0.31 0.04-0.03 0.03-0.31
10th Percentile 0.04 0.03 0.05 0.03 0.04 0.03 0.05 0.03 0.04 0.03
25th Percentile 0.00 0.03 0.06 0.03 0.05 0.03 0.07 0.03 0.06 0.03
75th Percentile 0.28 0.05 0.24 0.05 0.25 0.04 0.25 0.05 0.25 0.05
90th Percentile 0.47 0.09 0.45 0.06 0.45 0.00 0.48 0.10 0.45 0.07
Abbreviations: CV, coefficient of variation; Max, maximum; Min, minimum.
a. Concentrations were the average of spring and fall
data.
b. Includes both communities 1 and 2.
c. Methyl is sum of DMP, DMTP, and DMDTP concentrations.
d. Ethyl is sum of DEP and DETP concentrations. *p< 0.001
(Wilcox on matched- pairs signed-ranks test).
Eighty-six percent of the study children (83 children) had at least one
measurable DAP metabolite in the spring sampling, and 92% (88 children) had at
least one measurable DAP metabolite in the fall sampling. Only 1 of the 96
children had no measurable metabolites in either sample. DAP concentrations were
compared across seasons (spring and fall) for each community. We found no
significant differences for either dimethyl or diethyl concentrations (Wilcoxon
matched-pairs signed-ranks test, p > 0.05). We then averaged the two samples
from each child to represent the DAP concentrations during the study period
(May-November 1998). Table 1 provides descriptive statistics of DAP
concentrations in urine collected from the 96 focus children. We found no
significant differences or the median concentrations of either dimethyl or
diethyl DAP concentrations across communities (Mann-Whitney U-test, p > 0.05).
However, dimethyl DAP concentrations were higher than diethyl DAP concentrations
in both communities. Pooling data from the two communities, the median
concentrations of dimethyl and diethyl DAPs were 0.11 and 0.04 µmol/L,
respectively. Neither median dimethyl nor diethyl DAP concentrations were
significantly different between male and female children (Table 1; Mann-Whitney
U-test, p >.05). The boxplot in Figure 1 indicates that there
was no trend for age of the child and DAP concentration.
Figure 1. Dialkylphosphate (both dimethyl and diethyl) concentrations in
children living in the greater Seattle area grouped by age. Concentration trend
with age showed a nonsignificant difference (Kruskal-Wallis one-way ANOVA, p =
0.36 and p = 0.64 for methyl and ethyl DAP, respectively). Boxplot: the
horizontal lines in each plot represent 10th, 25th, 50th, 75th, and 90th
percentiles, bottom to top.
Eighty-six percent of the study children (83 children) had at least one
measurable DAP metabolite in the spring sampling, and 92% (88 children) had at
least one measurable DAP metabolite in the fall sampling. Only 1 of the 96
children had no measurable metabolites in either sample. DAP concentrations were
compared across seasons (spring and fall) for each community. We found no
significant differences for either dimethyl or diethyl concentrations (Wilcoxon
matched-pairs signed-ranks test, p > 0.05). We then averaged the two samples
from each child to represent the DAP concentrations during the study period
(May-November 1998). Table 1 provides descriptive statistics of DAP
concentrations in urine collected from the 96 focus children. We found no
significant differences or the median concentrations of either dimethyl or
diethyl DAP concentrations across communities (Mann-Whitney U-test, p > 0.05).
However, dimethyl DAP concentrations were higher than diethyl DAP concentrations
in both communities. Pooling data from the two communities, the median
concentrations of dimethyl and diethyl DAPs were 0.11 and 0.04 µmol/L,
respectively. Neither median dimethyl nor diethyl DAP concentrations were
significantly different between male and female children (Table 1; Mann-Whitney
U-test, p >.05). The boxplot in Figure 1 indicates that there
was no trend for age of the child and DAP concentration.
The reported residential pesticide use and the corresponding median DAP
concentrations in children are listed in Table 2. Forty-nine families (most in
community 2) reported having a garden, and 27 of them had applied pesticides in
the garden during the previous 6 months. Only one family reported use of
pesticides in the week preceding sample collection. Children living in a
household with a garden had significantly higher diethyl DAP concentrations than
those without a garden (Mann-Whitney U-test, p = 0.04). Children had
significantly higher DAP concentrations (both dimethyl and diethyl) when living
in households where garden pesticide use was reported (Mann-Whitney U-test, p =
0.05 and p = 0.02 for dimethyl and diethyl DAP, respectively). We found
significantly higher dimethyl DAP concentrations in children who had pets in the
household, but found no association for either dimethyl or diethyl DAP
concentrations and the use of pesticides on family pets. Twenty-three families
reported having their homes treated for fleas, cockroaches, or other insects,
and 45 families reported using pesticides on their lawns, but children's DAP
concentrations were not significantly different from those whose reported no
pesticide use. Figures 2 and 3 show
the boxplots of dimethyl and diethyl DAP concentrations in children's urine,
grouped by different residential use of pesticides. Analysis of data gathered
through parental interviews regarding child behavior and family hygienic
practices did not reveal any significant associations with DAP concentrations.
Table 2. Residential use of pesticides end the corresponding median
dialkylphosate concentrations (µmol/L) in children living in the Seattle
metropolitan area a
Question Dimethyl DAP concentration (µmol/L) Diethyl DAP concentration
(µmol/L)
Positive response (n)b Negative response (n)b p-Valuec Positive response
Negative response p-Valuec
Do you have a flower/vegetable garden?
0.14 (49)
0.09 (491
0.11
0.04
0.03
0.04
Do you apply any pesticides in your garden?
0.19 (27)
0.09 (22)
0.05
0.04
0.03
0.02
Do you apply any pesticides in your lawn?
0.14 (45)
0.09 (48)
0.13
0.04
0.04
0.68
Dow this household have any cats or dogs?
0.19 (40)
0.09 (56)
0.04
0.04
0.04
0.40
Are any of the following used on your cats and/or dogs? (flea powder, flee
ca deer, or shampoo)d
0.15 (18)
0.13 (18)
0.80
0.04
0.03
0.14
Since January 1990, has this home been treated for flies, fleas,
cockroaches, or other insects (this includes products like Raid, fly strips,
etc)? 0.11 (23) 0.11 (73) 0.35 0.03 0.04 0.27
a. Concentrations were the average of spring end fall data. Seattle
metropolitan area comprises communities 1 and 2.
b. Number of families who responded. Mann-Whitney U-Wilcoxon ran rank-sum W test.
c. Four families who owned a dog or cat did not answer
this question.
Figure 2. Residential use of pesticides and the distribution of dimethyl
dialkylphosphate concentrations (µmol/L) in children living in the Seattle
metropolitan area.
* (In garden) Significantly higher dimethyl DAP concentrations were found
in children whose parents reported use of pesticides in their gardens,
Mann-Whitney U-Wilcoxon rank-sum W test, p = 0.05.
Figure 3. Residential use of pesticides and the distribution of diethyl
dialkylphosphate concentrations (µmol/L) in children living in the Seattle
metropolitan area.
* (In garden) Significantly higher diethyl DAP concentrations were found
in children whose parents reported use of pesticides in their gardens,
Mann-Whitney U-Wilcoxon rank-sum W test, p = 0.02.
Discussion
This biological monitoring survey documents exposures to OP pesticides among
children living in urban/suburban communities. The use of urinary metabolites as
biomarkers provides an estimate of exposure by all routes (dermal, respiratory,
and oral) and assesses actual rather than potential absorption. Common urinary
metabolites that are identified after exposure to OP pesticides are the DAP
metabolites that are formed when OP pesticides undergo cleavage of the leaving
group with substitution for a hydrogen atom. Therefore, it is not possible to
attribute exposure to specific OP pesticides when using DAP metabolites without
detailed knowledge of sources and exposure pathways. Although a few specific
urinary metabolites exist (e.g., 3,5,6-trichloro-2-pyridinol for chlorpyrifos;
nitrophenol for parathion), they are not yet identified for most OP pesticides.
At least 39 OP pesticides are used in the United States, nearly all of which
produce DAP metabolites. Thus, the DAP metabolite method provides an integrated
exposure estimate for the OP pesticides. For the findings reported here, it is
likely that children's exposure to OP pesticides was the result of direct
exposure not only to agricultural OP pesticides in food but also to other OP
pesticides that are commonly used in residential environments.
Urinary metabolite measurements of environmental contaminants in adults are
routinely corrected for differences in urine flow rate by using creatinine
measurements or specific gravity. Normalization using creatinine is based on the
assumptions that creatinine concentration is inversely proportional to urine
flow and that creatinine excretion is independent of urine flow. However, it is
known that both exogenous (diet and exercise) and endogenous (age, sex, muscle
mass) factors can affect creatinine elimination (18). The increase in creatinine
excretion from infancy to adulthood correlates with the growth of muscle mass
and may further complicate the use of creatinine measurements. Because children
are a much less homogeneous population than adults, the appropriateness of
normalizing urinary metabolite values using children's creatinine measurements
is unknown at this point. Therefore, in this study, we used creatinine
measurements to determine the quality of urine samples, rather than to adjust
data.
Data obtained from the parental interview and follow-up questionnaire helped
identify factors that may influence a child's pesticide levels. In general, the
survey achieved its purpose of obtaining information relevant to the scope of
this study. Parents were able to answer most of the questions with certainty,
but some households provided much more detailed information in their responses
than did others. When parents were asked about residential pesticide use, they
were not normally able to provide information on the type of pesticide used and
the frequency of use. There may have been some recall bias in the reported
frequency of use of pesticides. Unless the application had occurred recently,
the parent had trouble remembering when and where a pesticide had been used. We
asked parents about home pesticide use within the previous 6 months. In many
cases, the parent did not know the name of the product used. Often the parent
being interviewed was not the parent who had applied the pesticides. If the
product was still on hand, we asked to see the product and then recorded
important information about the product, such as the active ingredients and the
EPA registration number. In some of the few cases where lawn services were used,
we were able to obtain information on products applied from the service.
The results from this study indicate that nearly all children sampled in the
Seattle metropolitan area had measurable DAP metabolites in their urine and that
70-75% had one of the two major metabolites (DMTP or DETP). The frequency of
detection of DAP metabolites in this study was greater than in our previous
study, in which a less sensitive analytical method was used for
DAP analysis (13). However, this result was within the range found by Hill and
colleagues (19), in which specific urinary metabolites for two OP pesticides,
chlorpyrifos and parathion, were measured in 82% and 41% of samples,
respectively, collected from 1,000 adults living in the United States.
The most striking finding from our study was the association between reported
residential pesticide use and elevated DAP metabolite concentrations in
children. Children whose families reported pesticide use in their gardens had
significantly higher diethyl DAP concentrations than those who had gardens but
did not use any pesticides. The association was also significant but weaker for
dimethyl DAP compounds. According to the administered survey and our
observations, 10 of 27 families who reported using pesticides in their gardens
used either chlorpyrifos or diazinon, both diethyl OP pesticides. We found this
association of increased DAP levels with OP pesticide use in the garden despite
the fact that the families may not have applied pesticides for months. Pesticide
residues residing in outdoor soil can be tracked easily into the indoor
environment and settle into the carpet along with other house dust, where it may
degrade more slowly (20,21). Ingestion of soil or house dust containing
pesticide residues may contribute to the exposure of young children because
children spend more time on the floor than adults and may engage in
hand-to-mouth and object-to-mouth behaviors.
Socioeconomic indicators, such as annual household income and housing type, were
not useful predictors of children's exposure to pesticides in this population.
One child's parents in community 2 reported buying exclusively organic produce
and did not use any pesticides at home. This child was the only subject whose
urine samples showed no measurable concentrations of any
of the DAP metabolites in the spring and fall samples. In this study, we found
no statistically significant differences in DAP levels during the spring and
fall. Many families who reported the use of pesticides during the spring
sampling period continued to use pesticides through the fall sampling period,
mostly in the garden. Depending on the climate in different regions in the
United States, pesticide use patterns in the residential environment may vary.
According to the 1997 Washington State Department of Health annual pesticide
incident report, 48% of reported health complaints were associated with
nonagricultural pesticide use and most incidents occurred during the spring and
summer months (22). A similar seasonal trend was suggested by a study conducted
to measure nonoccupational exposures to pesticides for residents of
Jacksonville, Florida, and Springfield, Massachusetts (23).
Neither age nor sex was associated with children's exposure to pesticides in
this study. In our previous study (13), a marginally significant trend of
increasing DMTP concentration was observed with decreasing age, suggesting that
activities associated with a child's age are an important variable for exposure.
The reasons for these conflicting results could stem from differences in the
communities where these children resided. In our previous study (13), children
were recruited from an agricultural community where agricultural pesticide was
used in close proximity to their homes and residential contamination was fairly
common, as evidenced by OP pesticide levels measured in house dust. If younger
children spent more time on contaminated surfaces in these homes than older
children, then the observed difference may have been real. A comparison between
2- to 5-year-old children and older children might help reveal such age
differences.
Meinert and colleagues (4) reported an association between residential
insecticide uses and childhood lymphoma (odds ratio = 2.6), and the frequency of
parental use of household insecticides was a significant factor for this
diagnosis (p = 0.02). However, the authors acknowledged that the lack of
insecticide exposure assessment was a major limitation of the study. A recent
study in rural El Salvador (14) evaluated OP pesticide exposure in children 8-17
years old, but yielded only qualitative data. The study found a significant
association between adult family member and child OP pesticide metabolite
concentrations, but other statistical analyses were confounded by the pooling of
adult and child data. Guillette and colleagues (24) found a difference in
physiological and neurological deficits in two groups of Yaqui Indian preschool
children, presumably due to pesticide exposure. The study was ecological in
design, and no measurements were taken of pesticides or any other toxicants that
might have affected the relative performance of the two groups. Therefore, the
attribution of the observed effects to pesticide exposure remains speculative.
Carefully conducted epidemiologic studies that incorporate biomonitoring are
needed to ascertain the health risks of pesticide exposure levels children.
The attribution of DAP metabolite measurements to specific pesticides is
difficult without detailed knowledge of exposure pathways (15), and such an
analysis is beyond the scope of this paper. Symptoms related to OP pesticide
exposure in this study were not specifically examined, but none were reported by
parents or children, and it is unlikely that the exposures observed in this
population would have caused acute intoxications. There is a lack of scientific
knowledge regarding the long-term health effects of low-level exposure to OP
pesticides in children. This study supports a public health recommendation that,
where possible, OP pesticide use should be avoided in areas where children are
likely to play. If a residential pesticide application is necessary, it is
important to follow the label instructions. Special caution should be taken to
avoid contamination of surfaces that are likely to be contacted by children and
other occupants.
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